[DRBD-user] DRBD 0.7.23 and MD corruption

Ross S. W. Walker rwalker at medallion.com
Wed May 23 18:16:25 CEST 2007

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.

> -----Original Message-----
> From: drbd-user-bounces at lists.linbit.com 
> [mailto:drbd-user-bounces at lists.linbit.com] On Behalf Of Lars 
> Ellenberg
> Sent: Wednesday, May 23, 2007 5:34 AM
> To: drbd-user at lists.linbit.com
> Subject: Re: [DRBD-user] DRBD 0.7.23 and MD corruption
> On Mon, May 21, 2007 at 05:20:40PM +0200, Lars Ellenberg wrote:
> > On Fri, May 18, 2007 at 11:56:33AM -0400, Ryan Steele wrote:
> > > I saw someone else post something similar to this a few 
> weeks ago, but 
> > > didn't see any response to it.  I've just set up DRBD 0.7.23 with 
> > > Heartbeat2 on two future database server.  However, DRBD 
> seems to have 
> > > corrupted my multi-disk RAID1.  I booted a Knoppix CD on 
> the affected 
> > > machines, removed the DRBD rc.d scripts, and rebooted and 
> things were 
> > > fine.  To verify, I ran update-rc.d to recreate the 
> symbolic links, and 
> > > rebooted again to find that it again would not boot.  
> Moreover, even 
> > > removing the rc.d links did not help - the array is, I 
> fear, irreparably 
> > > damaged.
> > > 
> > > Is there any acknowledgement of this bug, or are there 
> any suggestions 
> > > as to how one might go about fixing it?  I can't even 
> boot into the 
> > > machine to run mdadm and repair the array, though maybe I 
> can do that 
> > > from the Knoppix CD...
> > 
> > I think...
> > the issue is that md raid5
> wait. after reading your post closely again,
> you should not be affected by this.
> you said you use raid _1_ not raid5?
> hm...  so there may be something else?
> anyways.  drbd does not corrupt md raid (or anything, for that matter;
> I would have noticed for sure!) anywhere on boxes I was involved,
> or have access to.  and that are quite a few.
> so if this is a real issue for you, and you can reproduce 
> this at will,
> there is something "special" in your setup...
> try to _not_ mkfs /dev/something , then resize,
> but to mkfs /dev/drbdX ...
> try a different kernel, try with small arrays first, so you can more
> easily verify (by comparing against checksums/images) how/where
> the corruption takes place.  

Lars, et al,

I was wondering if a block storage device, which could exist on an MD,
were to be fully utilized before it was incorporated into a drbd
replication scheme would it also suffer from corruption.

Why I ask, is that I have a bunch of volumes used as iSCSI targets
that I am planning on replicating in the future, but are in production
today and wanted to know if it is safe to create replicas of these,
using a separate LV for meta-data?


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